The composite wire rod is known as a substitute for a PC-steel stranded, wire. The composite wire rod is formed by converting continuous fiber such as carbon fiber into composite fiber using thermoset resin such as epoxy resin and molding the composite fiber into a stranded wire such as 1×7. The composite wire rod has, like the PC-steel stranded wire, a high tensile strength and a high elastic coefficient and also features such a light weight and non-rusting properties. Making use of these features, the composite wire rod is used as repairing cables of existing bridges, reinforcing tendon of prestressed concrete beams and piles, post-tensioning bridge girder reinforcing materials and the like in the field of civil engineering, bridges and the like. When the composite wire rod is used for such uses, end fixing that grips both ends thereof is needed to tense the composite wire rod.
As an end fixing structure, a technology of a retention end of electric wire using resin reinforced carbon fiber as the core is known (For example, Jpn. Pat. Appln. KOKAI Publication No. 8-237840). That is, a buffer sleeve in a cylindrical two-split structure formed from metallic materials containing zinc or the like as the main component and having an engaging surface engaging with an outer circumference of the resin reinforced carbon fiber on an inner circumferential surface is used as the retention end of a stranded electric wire. In an electric wire in which resin reinforced carbon fiber is used as a tension member and a conductive metal wire is stranded therearound, a buffer sleeve is provided between the tension member and the conductive metal wire stranded layer, a metal sleeve is provided on the outer side thereof, and the metal sleeve is compressed and fixed to form the retention end. In this technology, the buffer sleeve has the engaging surface engaging with the outer circumference of the resin reinforced carbon fiber on the inner circumferential surface and has a two-split structure and so can easily be attached to the resin reinforced carbon fiber and is also molded in a cylindrical shape and so has an effect of preventing damage such as crushing and cracks of the resin reinforced carbon fiber because no local compressive force acts when the metal sleeve is compressed.
Also as the end fixing structure of a composite wire rod, a structure in which the composite wire rod is coated with an antislipping sheet, a blade made of metal is placed thereon, and this portion is fixed by being sandwiched between wedges is known (for example, Japanese Patent No. 5426678). This structure is provided with a function to grip the composite wire rod under high tension without causing damage by shearing due to buffer action by deformation of the antislipping sheet and the blade below the wedges in accordance with an irregularity portion of the composite wire rod when the wedges tighten the composite wire rod by an external force generated in the wedges when the composite wire rod is tensed and a frictional force by the antislipping sheet.
Further, a method of using, instead of the antislipping sheet, a composite cushioning material made of resin is proposed (for example, Japanese Patent No. 01-272889).